Linear self-synchronizing master-slave hydraulic remote control device

ABSTRACT

A plurality of manually operable master piston and cylinder assemblages and one or more slave piston and cylinder assemblages are connected in series with each other in a closed hydraulic circuit continuously pressurized at low pressure by way of an accumulator. Each master assemblage has a valving bypass circuit such that when the piston is manually driven it functions as a conventional piston. When it is driven by a differential in the fluid pressures applied to its opposite faces, it functions as a conventional piston until it closely approaches the ends of its strokes in opposite directions, respectively, whereupon the valving bypass circuit is rendered operative and bypasses the pressure fluid around the piston from one end of the cylinder to the opposite end. This renders the device self-synchronizing simply by manual movement of one of its master pistons through a complete forward and return stroke. Relief of excess pressures, and reduction of, and compensation for, thermal expansion and contraction are provided.

United States Patent [72] Inventors Donald A. Stark;

Ernest A. Di Bartolo; Harry A. Feather;

Charles H. Sundin, Sarasota, Fla. [21] Appl. No. 816,231 [22] Filed Apr. 15, 1969 [45] Patented May 25, 1971 [73] Assignee Fluid Controk, Inc.

Mentor, Ohio [54] LINEAR SELF-SYNCHRONIZING MASTER-SLAVE HYDRAULIC REMOTE CONTROL DEVICE 10 Claims, 8 Drawing Figs.

[52] US. Cl 60/54.5 [51] Int.Cl F15b 7/00 [50] Field of Search 60/54.5

[56] References Cited UNITED STATES PATENTS 2,292,916 8/1942 Wheelon 60/54.5X 2,368,659 2/1945 Heineck et a]. 60/54.5 2,410,978 11/1946 Kelly 60/54.5 2,657,536 11/1953 Levy 60/54.5 2,787,235 4/1957 Schroeder 60/54.6M 2,891,498 6/1959 Schroeder 60/54.5X 2,978,044 4/1961 Baines 60/54.5X 3,040,533 6/1962 Heinrich... 60/54.5 3,242,675 3/1966 Norton 60/54.5

3/1968 Hebel etal OTHER REFERENCES HYDRAULIC I-lANBOOK-TRADE AND TECHNICAL PRESS, LTD. SECOND EDITION-Page 213-Copy in Group 340.

Primary Examiner-Martin P. Schwadron Assistant Examiner-A. MI Zupcic AttorneyJohn H. Leonard ABSTRACT: A plurality of manually operable master piston and cylinder assemblages and one or more slave piston and cylinder assemblages are connected in series with each other in a closed hydraulic circuit continuously pressurized at low pressure by way of an accumulator.

Each master assemblage has a valving bypass circuit such that when the piston is manually driven it functions as a conventional piston. When it is driven by a differential in the fluid pressures applied to its opposite faces, it functions as a conventional piston until it closely approaches the ends of its strokes in opposite directions, respectively, whereupon the valving bypass circuit is rendered operative and bypasses the pressure fluid around the piston from one end of the cylinder to the opposite end. This renders the device self-synchronizing simply by manual movement of one of its master pistons through a complete forward and return stroke. Relief of ex cess pressures, and reduction of, and compensation for, thermal expansion and contraction are provided.

PAIENTEUMAY25|97| 9579.999

SHEET 1 [IF 4 2a 2b INVENTORS.

DONALD A. STARK H 5 ERNEST A. 0| BARTOLO HARRY- A. FEATHER CHARLES H. SUNDIN I 2 71a;- ATTORNEY miminmzslsn 3.579989 SHEET E OF 4 o 34 IN NTORS DONALD A.STAF\ ERNEST A. Di BARTOLO HARRY A. FEATHER CHARLES H. UN DI I Jy MN I j ATTORNEY.

PATENTED A125 197i V 3 579.989

' sum u 0F 4 IZI INVENTORS.

DONALD A. STARK ERNEST A.Di BARTOLO HARRY A. FEATHER CHARLES H. SUNDIN ATTORNEY.

LINEAR SELF-SYNCHRONIZING MASTER-SLAVE HYDRAULIC REMOTE CONTROL DEVICE This invention relates to a multistation linear master-slave hydraulic remote control device comprising a slave piston and cylinder assemblage operable by each one, selectively, of a plurality of manually operable master piston and cylinder assemblages located at various control stations remote from each other and connected in series with each other and with the slave cylinder assemblage in a closed hydraulic circuit pressurized at low pressure.

Generally, each control device comprises one slave assemblage and a plurality of senders or master assemblages, the number of senders being as many as desired by the particular user. In some instances, a single control assemblage may include a plurality of slave assemblages. Regardless of the number of master-slave assemblages employed in a given device, all of the cylinders thereof are connected in series with each other and with the cylinder of the slave assemblages in a single hydraulic circuit pressurized at low pressure.

If a plurality of mechanisms are to be individually controlled remotely, separate multistation remote control devices such as the one herein illustratively disclosed are used, one for each mechanism.

'The invention is specifically disclosed herein for purposes of illustration as arranged for the control of a throttle of a boat engine from either of two control stations, selectively, each control station being provided with a sender or master piston and cylinder assemblage and the master assemblages being connected in a closed hydraulic circuit in series with each other and with a single slave piston and cylinder assemblage which, in turn, is drivingly connected to the throttle.

An important feature of the invention is that the synchronization of the piston and cylinder assemblages is obtained readily by manually operating the piston of any selected one of the master piston and cylinder assemblages through one complete cycle of forward and return strokes.

The hydraulic fluid and the piping of the hydraulic circuit are so related that the effects of differentials in thermal expansion and contraction of one relative to the other are negligible. Excessive pressures are automatically relieved.

The present device is free from backlash so that the slightest movement of a selected master piston is accurately reflected at the throttle or mechanism to be controlled. Thus the control device can maintain constant operation of the controlled mechanism; for example, constant engine speed, a feature which is especially important on multiengine boats, as it eliminates drift. The maintenance is minimal and the installation simple.

Various specific objects and advantages of the invention will become apparent from the following description wherein reference is made to the drawings in which:

FIG. 1 is a schematic illustration showing the operating elements and circuitry of the present invention;

FIG. 2 is an enlarged front elevation of the principal components and circuitry of the present invention, part of the components being shown in section for cleamess in illustration;

FIG. 3 is an enlarged longitudinal sectional view through one of the pistons of a master piston and cylinder assemblage of the present invention, showing the valving bypass circuit of the assemblage;

FIG. 4 is a fragmentary sectional view takenon the line 4-4 in FIG. 2;

FIG. 5 is a schematic illustration of a modified form of the device of FIG. 1 in which two slave piston and cylinder assemblages are employed in the circuit;

FIG. 6 is a diagrammatic illustration showing a structure similar to FIG. I wherein the valving bypass circuit and slave relief circuit are arranged externally of the cylinders;

FIG. 7 is a modification similar to FIG. 1 wherein the master assemblages are of the single rod piston type; and

FIG. 8 is a further modification of the invention for use in connection with a single master and slave remote control.

Referring to FIG. I, the invention comprises duplicate master piston and cylinder assemblages 1 and la, respectively, which are connected to a slave piston and cylinder assemblage 3. Since the master piston and cylinder assemblages may be identical, both in form and function, only the master assemblage 1 is described herein in detail, the corresponding parts of the assemblage la being indicated by like reference numerals with the suffix a.

The master or sender piston and cylinder assemblage 1 comprises a cylinder 5 closed at one end by a sleeve plug 6 and at the other end by a sleeve plug 7. Mounted within the cylinder is a piston 8 having a piston rod 9 which extends entirely through the piston and out through the sleeve plugs 6 and 7, respectively, at opposite ends of the cylinder. The plugs 6 and 7 are suitably sealed in the ends of the cylinder 5 and carry suitable bearing sleeves 10 and 11 for the piston rod. Suitable O-ring seals and packing are provided to assure fluidtight seals between each plug and the cylinder 5 and between each plug and its associated bearing sleeve and associated portion of the piston rod.

The piston 8 is arranged to be driven by external means, such as a manual rock lever 12. The lever 12 is fixedly mounted on a rotatable hub 13 and carries a connecting rod 14 which, at its outer end, is pivotally connected to one end of a link 15 by a pivot 16. The other end of the link 15 is pivotally connected by a pivot 17 to one end of the piston rod 9. For convenience in mounting the assemblage 1 and its rock lever 12 at a control station, a housing 18 is provided which can be mounted in fixed position on the boat, as by suitable bolts or lag screws. The cylinder is secured to the housing 18 by suitable bolts or tie rods 19.

The cylinder is provided at opposite ends with fittings 20 and 21, respectively, by which it is connected in the closed hydraulic circuit. One of these fittings is provided with a normally closed bleeder valve 22 used in purging the circuit of air when necessary. The fittings 20 and 21 are connected with the interior of the cylinder through suitable ducts 23 and 24, respectively, in the sleeve plugs 6 and 7.

The master piston and cylinder, as thus far described, is in general, conventional, and lacks any means for selfsynchronization such as later to be described herein.

The; slave piston and cylinder assemblage 3 comprises a cylinder 30 closed at its ends by sleeve plugs 31 and 32, respectively, which are connected in sealed relation in the ends of the cylinder. Mounted within the cylinder is a slave piston 33 having a rod 34 extending from opposite faces thereof and through suitable sealing sleeves 35 and 36 in the plugs 31 and 32, respectively. The plugs 31 and 32 are in leakproof sealed relation to the cylinder 30, to the sleeves 35 and 36, and to piston rod 34. The rod 34 extends beyond opposite ends of the cylinder 30 and is connected at one end to a ball and socket connecting assembly 37 having a ball 38 which is connected to a control rod 39 of a throttle 40 of a boat engine, or other mechanism to be controlled, for driving it in opposite directions upon opposite directions of endwise movement of the slave piston 33.

The cylinder 30 is provided with fittings 50 and 51 which are connected to the opposite ends of the cylinder through suitable counterbores 52 and 53, respectively. Each of the fittings 50 is adapted for connection to a conduit of the hydraulic circuit. The fittings 50 and 51 have bleeder valves 54 and 55, respectively, for use in purging the circuit. The slave cylinder may be secured in the desired position on the boat by a suitable bracket 56.

The master assemblages 1 and 1a, and the slave assemblage 3 thus described, connected in series with each other, could be used as a simple nonsynchronizing multistation master and mal expansion and contraction of the hydraulic fluid and various parts of the circuitry, and automatic replacement of leakage fluid is effected.

For connecting the master assemblages l and la and the slave assemblage 3 in series, the fitting 21 of the master cylinder is connected by a tube 60 to the fitting 50 of the slave cylinder 30. The fitting 51 of the slave cylinder 30 is connected to the fitting a of the master cylinder 5a by a tube 61. The fitting 21a of the master cylinder 5a is connected by a tube 62 to a relief valve assembly 63 which, in turn, is connected to the fitting 20 of the master cylinder 5, as later described herein. Makeup fluid is continuously supplied under pressure to the relief valve assembly 63 from a pressurized accumulating reservoir 64.

The relief valve assembly 63 includes a hollow body 65 having an inlet 66 which is connected by a tube 67 to the reservoir 64. Within the body 65 is a spring seated low-pressure check valve 68 which is operable by pressure fluid from the reservoir 64 so as to discharge into suitable interconnecting ducts 69, one of which is connected by a tube 70 to the fitting 20 of the master assemblage l and the other of which is connected by the tube 62 to the fitting 21a of the master cylinder la. The valve 68 is openable by relatively low pressure, for example, 6 p.s.i., so as to permit hydraulic fluid to flow readily from the inlet 66 therepast. It seems to prevent return flow.

Within the body 65 is a high-pressure relief check valve 75 which includes a check valve plug 76 seated by a spring 77, and which, for example, may open at a pressure of about 150 p.s.i. This valve is arranged to open in a direction away from the ducts 69 and toward the reservoir 64 so that if the pressure in the circuit increases beyond that permissible, the valve 75 relieves the excess pressure by admitting fluid from the circuit into the reservoir 64.

The reservoir 64 comprises, in general, a cylinder 77 having at the bottom a fitting 78 connected to the tube 67. A suitable screen 79 is provided over the inlet to the fitting 78. At the opposite end the cylinder 77 is provided with a removable filling plug 80, with an air inlet valve and stem 81 such as a conventional tire valve and stem, and with a pressure gauge 82. The cylinder can be filled to a desired level with fluid, the plug 80 sealed in place, and air admitted through the valve 81 to charge the cylinder to the pressure desired, for example, about 30 p.s.i. Assuming that the valve 68 opens at 6 p.s.i., the reservoir provides a source of makeup pressure fluid under light positive hydraulic pressure continuously connected to the closed circuit.

One of the most important features of the invention is the self-synchronization, and this is obtained by the valving arrangement and valving bypass circuitry now to be described.

For this purpose, the valving arrangement and bypass circuitry is, in general, such that when either of the master pistons 8 or 8a is operated by its lever 12 or 120 or by fluid pressure in an intermediate position spaced appreciably from either end of its associated cylinder, the flow of fluid from one end of its associated cylinder to the other end in bypassing relation around the piston is prevented and blocked, so that the position functions as does a conventional solid piston. The valving arrangement and bypass circuitry is such that when either piston 8 or 80 is moved manually by its lever 12 or 12a in either direction endwise of its cylinder, the valving arrangement and bypass circuitry remains operative to prevent the bypass of the'fluid in the cylinder from one side of the piston to the other. On the other hand, when either piston 8 or 80 is driven by a differential in the fluid pressures applied to its opposite faces, it operates as a conventional piston only until it nears the end of its stroke, whereupon the valving bypass circuitry is rendered operative to permit the hydraulic pressure fluid to bypass from one end of the cylinder past the piston to the other end.

A particularly desirable valving bypass circuit for each master assemblage is one incorporated in the piston itself. In the illustrative example, this is accomplished by a combination of certain ducts and check valves, ordinary automobile tire valves 84 being preferable. A suitable tire valve 84 is illustrated in FIG. 3, and comprises a body 85 having a central passage 86 extending therethrough. The body has an enlarged diameter screw portion 87 by which it is secured in operating position. On one end of the body is an annular seat 88 coaxial with, and in communication with, the passage 86. A stem 89 is mounted, with clearance, in the passage 86 and carries at its inner end a valve plug 90 which is normally seated on the seat 88 by means of a low pressure seating spring 91. The valve plug 90 can be unseated against the resistance of the spring by fluid at relatively low pressure entering the passage 86 at the end thereof in the portion 87, or by pressing inwardly endwise of the piston on the outer end of the stem 89.

The piston has two bores 92 which are open at their outer ends through opposite faces, respectively, of the piston 8. Each is closed at its inner end. At their open ends the bores are internally threaded for threaded connection with the portions 87 of the valve bodies 85, respectively. Each valve 84 is normally closed and is provided with an external annular seal 94 which effects a sealed relation between its body and the wall of its associated bore 92 at the location between the valve seat 88 and the open end of the bore 92. The valves are installed in the bores 92 in the piston with their stems 89 projecting outwardly beyond the opposite faces, respectively, of the piston, each at the open end of its associated bore. The projecting distance is such that when the piston has reached a predetermined position near the end of its stroke in the direction in which the particular stem projects, that stem 89 is engaged by the adjacent end wall of the cylinder. Upon continued movement of the piston in the same direction, the stem is depressed and unseats its associated plug 90. When unseated, free communication for pressure fluid is provided between the associated bore 92 beyond the seat in the unseating direction and the end of the cylinder into which the particular stem projects.

A suitable duct 95 in the piston interconnects the inner ends of the bores 92 at the plug side of their respective seats 88. Thus any fluid entering either bore 92 at its outer end can pass to the other side of the piston only by way of the duct 95 and the other bore 92.

Referring to FIG. 2, it is apparent that if the piston 8 is moved upwardly or downwardly by operation of the lever 12, it operates as though no bores 92 and valves 84 were present. If thus moved in either direction by the lever 12, a higher fluid pressure is developed in the end of the cylinder toward which the piston is advanced. This can unseat the valve 84 of which the stem 89 projects toward that end of the cylinder, but such pressure seats even more firmly the other of the two valves 84. However, when the piston is moved by a differential in pressure fluid, instead of by the manually operated rock lever 12, a different valving operation occurs. For example, referring to FIG. 2, the piston 8 may be moved downwardly by higher fluid pressure on its upper face than on its lower face. This higher pressure, of course, can open the valve 84 with the upwardly projecting stem 89, but assures firm sealing of the valve 84 with the downwardly projecting stem 89, so that the piston operates as a solid piston. When, however, the piston is driven sufficiently far downwardly by fluid pressure so that the downwardly projecting valve stem 89 engages the lower end wall of the cylinder, this particular valve 84 is opened against the force of its spring and of the higher pressure at the upper side of the piston. Since the valve 84 with the upwardly projecting stem is opened by fluid pressure and the one with the downwardly projecting stem is opened by an upward thrust on the lower end of its stem, a completely open bypass is provided which can bypass the pressure fluid from the cylinder at one face of the piston 8 into the portion of the cylinder 5 at the opposite face via the bore 92 and duct 95. A corresponding valving sequence occurs when the piston 8 is moved upwardly by a positive differential of fluid pressure applied at its lower face, the piston initially acting as a solid piston until the valve 84 with the upwardly projecting stem 89 is opened by engagement of its stem with the upper end wall of the cylinder.

The slave piston 33 is provided with two normally closed check type valves 96, each similar to the valve 84 heretofore described, except that it has a stronger spring and requires a higher fluid pressure differential for opening. Each should open at a pressure differential lower than required for opening the relief valve 76.

The valves 96 also may be high-pressure tire valves. They open in opposite directions and are spring seated as described. However, they are mounted in the piston 33 so that their stems 97, if any, do not project beyond the respective faces of the piston and cannot engage the plugs 31 or 32 in the ends of the slave cylinder 30. Consequently they can be unseated only by a differential in pressure of the fluid at opposite faces of the piston. The valves 96 are mounted in bores 98, respectively, and each bore extends entirely through the piston 33 independently of the other. Thus each valve can be opened by the requisite fluid pressure introduced at the stem side of its seat and bypass fluid through the piston independently of the other valve. As mentioned, valves 96 of the slave piston require a much higher fluid pressure for opening than the valves 84 heretofore described. For example, while the valve 84 may be opened by a differential in fluid pressure of about 6 psi. directed through the seat in the unseating direction of the plug, the valves 96 are arranged to open at a fluid pressure of, for example, about 100 psi. and their stems are arranged so that they cannot be engaged and caused to open the valves.

Referring to FIG. I, to charge the system, the reservoir 64 is charged with fluid and placed under sufficient pressure to feed pressure fluid to the lower end of the left-hand cylinder 5, thus driving its piston 8 upwardly its bleeder 22 being operable to bleed out air during this operation. The piston 8 rises until its bypass circuit is opened by engagement of the upwardly projecting valve stem 89 with the upper end wall of the cylinder. Thereupon the pressure fluid passes through the piston 8, upper end of the left-hand cylinder 5, and tube 60 to the lefthand end of the slave cylinder 30. Air is bled out from the lefthand end of the cylinder 30 through the bleeder 54.

Pressure fluid is fed through the tube 62 to the upper end of the right-hand cylinder 5a, air being bled out by the bleeder 21a until the upper end of the cylinder 5a is filled and the piston 80 is moved downwardly. When the piston 8a reaches the bottom of its stroke, its bypass circuit is opened by engagement of its downwardly projecting valve stem with the bottom wall of the cylinder 5a, and pressure fluid flows readily into the lower end of the cylinder 50 and out through the fitting 200 through the tube 61 to the right-hand end of the slave cylinder 30, air being vented continuously by the bleeder 55. Preferably theslave cylinder is bled first at one end and then at the other. When the system appears to be full of hydraulic fluid and is purged of air the bleeders are closed. The plug 80 in the reservoir is removed and the fluid in the reservoir 64 is brought up to the proper level, whereupon the plug is returned and sealed and air pressure is admitted through the valve 81 on top of the fluid so as to maintain the desired positive pressure of the fluid at all times; for example, about 30 psi. In this condition, of course, the system is not synchronized to place the master pistons in identical positions in their respective cylinders and in the proper relation to' the position of the slave piston.

In order to synchronize the control device, all that is necessary is to operate one of the rock levers 12 or 12a so as to move its associated piston 8 or 80 slowly, but firmly, through an entire advance stroke in one direction and then an entire return stroke in the opposite direction. For example, assume that the pistons 8 and 8a are in relatively different intermediate positions, as also is the slave piston 33. The piston 8 may be driven to the upper end of its stroke by its rock lever 12. The pressure fluid expelled from its upper end is delivered to the left end of the slave cylinder 30 and drives the slave piston 33 to the right. The slave piston may be moved fully or only partway to the right-hand end of its stroke. However, as it moves the pressure fluid expelled from the right-hand end of the slave cylinder 30 passes to the lower end of the cylinder 5a and drives the piston 8a upwardly. If the piston 8a moves entirely to the upper end of its stroke before the completion of the upward movement of the piston 8, the bypass circuitry through the piston 8a is opened and any excess fluid being delivered to the lower end of the cylinder 5a bypasses the piston 80 and passes through the upper end of the cylinder 5a to the lower end of the cylinder 5. Thus both master pistons are synchronized with respect to each other at the upper ends of their respective strokes, but are not synchronized with respect to the slave piston.

If, on the other hand, the master piston 8a is not moved to the upper end of its stroke by movement of the piston 8 to the upper end of its stroke, then the two are not synchronized with respect to each other.

Next, the piston 8 is driven by its rocker 12 to the bottom of its stroke. Since the lower end of the cylinder 5 is now filled to capacity with pressure fluid, then, as the piston 8 is moved downwardly to the lower end of its stroke, a full charge of pressure fluid is delivered to the upper end of the cylinder 50 and drives the piston 8a entirely to the bottom of its stroke. Since the piston 8a was already partway down toward the bottom of its stroke, there is an excess of fluid delivered to the. upper end of the cylinder 5. However, when the piston 8a reaches the lower end of its stroke, its valving bypass circuitry opens and the excess of fluid being delivered from the lower end of the'cylinder 5 to the upper end of cylinder 5a passes through the piston 8a and lower end of the cylinder 5a to the right-hand end of the slave cylinder 30. Thus, a full charge of fluid is delivered to the right-hand end of the slave cylinder 30 and assures that the slave piston 33 is driven entirely to the left end of the slave cylinder 30.

Since it started from a position spaced from the left end of the cylinder 30, the piston 33 may reach the left end before the piston 8 and 8a have reached the bottom ends of their strokes. In such case, due to the application of force on the lever 12, higher pressure is developed in'the excess fluid at the right end of the slave cylinder 30 and opens one of the relief check valves 96 through the piston 33, allowing the excess fluid to bypass the piston 33 and pass to the upper end of the cylinder 5. At the end of this operation, therefore, the pistons 8 and 8a have reached the ends of their downward strokes and the slave piston 33 has traveled to the left to the end of its stroke. Thus, all pistons and cylinders are synchronized.

Again, assume that upon driving the piston 8 to the upper end of its stroke, the slave piston 33 reaches the right-hand end of its stroke before the master piston 8 has reached the upper end of its stroke. In such an instance continued movement of the piston 8 upwardly forces pressure fluid from the upper end of the cylinder 5 into the left-hand end of the cylinder 30 and opens the opposite one of the relief check valves 96 in the piston 33, permitting any excess fluid to pass to the lower end of the cylinder 50. If the fluid supplied to the lower end of the cylinder 5a is inadequate to drive the piston 8a to the upper end of its stroke, then upon downward movement of the piston 8 to the lower end of its stroke, the piston 8a would be moved to the bottom of its stroke and thereby synchronized with respect to the piston 8, and any excess of fluid from the cylinder 5 would bypass the piston 8a and pass to the slave piston 33 and drive it to the left end of its stroke,

' thus synchronizing all piston and cylinder assemblages. Any

over-volume of fluid in the circuit due to expansion is relieved through the valve 76 into the accumulator. Upon subsequent cooling and contraction of the fluid, this is fed back from the accumulator through the valve 68.

If at any time, due to leakage and the like, the system should become unsynchronized, one complete cycle operation of either master cylinder by its manual lever will rectify the situation. It is preferable that, with all pistons centered in their respective cylinders, the volumetric capacity of each cylinder at each side of its piston is equal and is equal also to the volumetric capacities at each of the opposite sides of the piston of each of the other cylinders.

In order to minimize difficulties in expansion, contraction and the like, the connecting conduits or tubes described are preferably of plastic tubing having a coefficient of expansion as near as may be equal to the coefficient of expansion of the hydraulic fluid. As an example, Nylon tubing may be used with a water and antifreeze mixture such as one part of glycol-type permanent antifreeze to one part of water.

The circuit is maintained closed and pressurized at about 30 p.s.i., as mentioned, by air above the fluid in the reservoir 64. The system is purged by purging first through one slave bleeder and then the other. When the level of hydraulic liquid in the reservoir drops below a predetermined level, additional fluid is introduced thereinto.

In purging the master assemblages, the one which is located at the lowest elevation is purged first, followed by purging of the successively higher assemblages. Having thus purged the system, movement of one of the control levers slowly but firmly through an entire stroke, first in one direction and then in the other, synchronizes the system. If there is not a flrm response, then the purging operation is repeated.

The arithmetically recited value for spring and fluid pressures in the above examples are for illustration only. These arithmetical values may vary depending upon the requirement of the particular mechanism which the system is to control but the value selected must be such as to maintain the proper functional interrelations described.

Should it be desired to operate a plurality of slave assemblages from a given group of master assemblages, then, as indicated in FIG. 5, the master assemblages, indicated at lb and 1c, and slave assemblages indicated at 2a and 2b are all connected in series. The circuitry and valving in all other respects correspond to like parts in FIGS. I through 5.

However, it is preferable that when more than one slave assemblage is used, each one which is in excess of the one, such as the assemblage 3 described in connection with FIG. 1, should employ valving bypass circuitry such as used in the master pistons instead of higher pressure relief valves such as valves 96.

Referring next to FIG. 6, a structure similar to that of FIG. 1 is shown diagrammatically. In this modified form, the valving bypass circuitry is arranged exteriorly of the cylinders instead of being incorporated in the pistons thereof.

As illustrated, two master piston and cylinder assemblages, designated generally at 100 and 100a, respectively, are shown connected to a single slave piston and cylinder assemblage 101. The assemblages 100 and 100a are duplicates and hence only the assemblage 100 is described in detail, the like parts in the assemblage 100a being indicated by like numerals with the suffiX a.

The assemblage 100 comprises a cylinder 102 having a double rod piston 103 which may be hand operated by a lever 104 similar to the lever 12 of FIG. 1. At the upper end of the cylinder 101 a spring seated check valve 105 having a stem 106 is provided, and is arranged to be opened by predetermined pressure of fluid in the upper end of the cylinder 102 or by engagement and upward movement of its stem 106. The stem 106 extends into the upper end of the cylinder 102 so that it can be engaged by the piston 103 and moved upwardly to unseat the valve 105 when the piston is moved substantially to the upper end of the cylinder 102.

A similar valve 107 is connected to the lower end of the cylinder 102 and has a stem 108 in a position to be engaged by the piston 103 when the piston is moved substantially to the bottom of the cylinder 102. The valve 107 is openable by the predetermined fluid pressure in the lower end of the cylinder or by engagement of its stem 108 by the piston 103. The valves 105 and 107 are connected together at the outlet sides of their seats by an external pipeline or tube 109.

Both of the assemblages I and 100a are connected in series with the slave assemblage 101 in the same manner as are the assemblages 1 and la in FIG, 1.

The slave assemblage comprises a cylinder 110 in which a double rod piston 111 is reciprocable. A pressure relief bypass circuit is provided around the piston by means of oppositely opening spring seated pressure relief check valves 112 and 113 connected in parallel with each other and with the parallel circuit of the two connected to opposite ends of the cylinder 110, respectively, as indicated.

A main pressure relief valve assemblage 114 with a makeup fluid reservoir 115, corresponding to the relief valve assemblage 63 and reservoir 64 illustrated in FIG. 2, are provided and are connected in the circuit for assuring that the circuit remains filled with pressure fluid.

Except for the fact that the valving bypass circuits are arranged externally of the respective cylinders, the circuitry used is the same as that illustrated in FIG. 2.

Referring next to FIG. 7, a structure similar to that of FIG. 2, except that the master piston and cylinder assemblages employ single rod pistons, respectively, is illustrated.

In this modification, the master piston and cylinder assemblages 116 and 116a are provided. Referring specifically to the master assemblage 116, it comprises a cylinder 117 in which is reciprocable a piston 118 having a single rod 119. The valving bypass circuitry is the same as that illustrated in FIG. 2 and comprises two spring seated check valves 120 which have stems extending endwise outwardly from the opposite faces of the piston 118, respectively. These assemblages are connected to the slave piston and cylinder assemblage 121 which comprises a cylinder 122 in which is reciprocable a piston 123 having rods 124. The piston has pressure relief valves 125 corresponding to the valves 96 of the slave assemblage 3 in FIG. 2.

In this structure the rod ends of the assemblages 116 and 116a are connected by tubes 126 and 127 to opposite ends of the slave cylinder 122. The head ends of the cylinders 117 and 117a are directly connected to each other by a tube 128. A high-pressure relief valve assemblage 129 and makeup reservoir 130, corresponding in function to the valve assemblage 63 and reservoir 64 of FIG. 2, are connected to one of the pipe lines or tubes, such as the tube 126.

In this modification, as the piston 118a of the assemblage 1 16a is moved upwardly toward the rod end, the fluid expelled from the upper or rod end of the cylinder 117a is passed to the left end of the slave cylinder 122 and drives the piston 123 to the right, expelling pressure fluid from the right end of the slave cylinder 122 to the lower or rod end of the inverted cylinder 117. This, of course, drives the piston 118 upwardly, the same distance that the piston 1180 is driven upwardly. The effective areas of the rod ends of the pistons 118 and 118a are equal and the areas of the head ends are equal. Since the as semblages are reversed in position, the movements of the pistons 118 and 118a are equal and in the same direction.

Assuming the assemblages 116 and 116a are provided with levers 131 and 131a, operating in the same manner as the lever 12 in FIGS. 1 and 4, then the outer end of the lever 131 moves downwardly the outer end of the lever 131a also moves downwardly.

Since the cylinders 117 and 117a are connected at their rod ends to the opposite ends, both of which are rod ends, of the slave cylinder 122, the piston 123 is moved the same distance as each of the pistons 118 and 118a. The effective area of each end of the piston 123 is, of course, equal to the effective area of each of the rod ends of the pistons 118 and 118a.

This modification employing master assemblages with single rod pistons is useful in that, in each cylinder, there is only one movable sealed joint, this being between the single piston rod and the adjacent end wall of the cylinder. Thus only a single packing is required and hence leakage and friction are reduced. The master assemblages are lower in cost and require less space.

Referring next to FIG. 8, this modification combines a single master piston and cylinder assemblage with a single slave piston and cylinder assemblage. It is convenient for simple remote controls.

In this structure, either assemblage may be used as the slave and the other as the master. For purposes of illustration, an assemblage 135 is shown as the master. ln this assemblage, a cylinder 136 is provided with a piston 137 having a single rod 138. The piston 137 may be driven by a suitable lever 139 connected to the rod 138. The opposite ends of the cylinder 136 are connectable to each other through normally closed valving bypass circuitry which includes two oppositely opening spring seated pressure relief check valves 140 and 141 connected in parallel with each other and to opposite ends of the cylinder 136.

In this form, the parallel connection is obtained by mounting these valves 140 and 141 in the piston 137 in the same manner as the relief valves are mounted in the slave piston 33 of FIG. 2.

The slave assemblage 142 comprises a cylinder 143 in which is reciprocable a piston 144 having a single rod 145. The rod end of the cylinder 136 is connected to the rod end of the cylinder 143 and the head end of the cylinder 136 is connected to the head end of the cylinder 143. A high-pressure relief valve 146 and makeup reservoir 147 are connected in the circuit; for example, to the head ends of the cylinders 136 and 143. In this form of the invention, the valves 140 and 141 may be tire valves, if desired, but if so, their stems do not protrude beyond the associated faces of the piston. Thus they can be opened only by the pressure of the fluid exceeding by a predetermined amount the pressure required for operating the piston 144.

Upon downward movement of the piston 137, the pressure fluid expelled from the head end of the cylinder 136 is passed to the head end of the cylinder 143, thus moving the slave piston 144 the same distance to the left as the distance the piston 137 is moved downwardly.

Conversely, upon upward movement of the piston 137 the pressure fluid from the rod end of the cylinder 136 is fed to the rod end of the cylinder 143, thus returning the piston 144 to the right the same distance as the piston 137 is moved upwardly.

ln event the piston 144 bottoms first, continued pressure in the same direction applied on the piston 137 by the lever 139 exceeds the opening pressure of the appropriate one of the valves 140 and 141, allowing the excess pressure fluid in the cylinder 136 to bypass the piston 137 to the end of the cylinder away from which the piston is being moved.

This structure provides a very simple remote control in which the two assemblages can be synchronized readily by operating either piston as a master through one complete cycle.

Having thus described our invention, we claim:

1. A linear self-synchronizing master-slave remote control comprising:

a plurality of reversible, hydraulic power generating, master piston and cylinder assemblages and a reversible slave piston and cylinder assemblage responsive to the hydraulic power generated by the master piston and cylinder assemblages;

each assemblage including a cylinder having an inlet and an outlet and a piston reciprocable in the cylinder;

operators mechanically connected to the master pistons, respectively, and movable independently of each other, each in opposite directions, selectively, for thereby driving its associated piston in opposite directions, selectively, for generating hydraulic power;

means for connecting the slave piston to a mechanism to be driven thereby;

conduits connecting all of the cylinders in series in a closed hydraulic circuit;

bypass circuits in the master assemblages, respectively, each bypass circuit, when open, connecting the opposite ends of the associated master cylinder directly to each other;

a pair of normally closed check valves in series with each other in each bypass circuit and having spring seated plugs, respectively, and being operative upon concurrent unseating of both plugs to open their associated bypass circuit;

the check valve plugs of each pair unseating in opposite directions relative to the flowof fluid through their associated bypass circuit so that a differential in fluid pressure in the associated master cylinder drives the piston thereof away from the higher pressure end of the cylinder toward the lower pressure end of the cylinder, and urges to unseated position the one of the plugs nearest the higher pressure end of the cylinder along the path of flow through the bypass circuit, and urges the plug nearest the low-pressure end of the cylinder along said path of flow to seated position;

mechanical trip means associated with the master assemblages, respectively;

the mechanical trip means of each master assemblage being operative upon movement of the piston thereof a predetermined distance toward the lower pressure end of the cylinder thereof, to engage and unseat mechanically the one of the associated plugs which is urged to seated position by said differential in fluid pressure;

a slave cylinder bypass circuit in the slave assemblage and operative when open to connect opposite ends of the slave cylinder to each other; and

a pair of normally closed check valves in the slave cylinder bypass circuit, each valve having a spring seated plug, and said plugs normally closing the slave cylinder bypass circuit, one of said plugs being unseatable and thereby opening the associated bypass circuit and the other being urged concurrently to seated position by a fluid pressure differential above a predetermined normal operating differential in the slave cylinder at one side of the slave piston; the other of said plugs being unseatable and thereby opening the associated bypass circuit and the one plug being urged concurrently to seated position by a fluid difierential pressure above said predetermined normal operating differential in the slave cylinder at the opposite side of the slave piston.

2. The structure according to claim 1 wherein, in each master assemblage, unseating stems are connected to the plugs, respectively, of the check valves;

said stems are exposed at opposite sides, respectively, of the I piston; and

said mechanical trip means include trip members in the cylinder at opposite sides of the piston, respectively; each member is engageable with the associated stem, which is exposed at the same side of the piston as the trip member, so as to move the engaged stem to plug unseating position upon movement of the piston a predetermined distance toward the end of the cylinder on the same side of the piston as the associated member and stem.

3. The structure according to claim 2 wherein the bypass circuit of each master assemblage comprises a passage extending endwise through the piston, said check valves are mounted in the passage so as to be in sealing relation thereto when in closed position; the stem of one check valve extends out of one end of the passage beyond the adjacent face of the piston;

and

the stern of the other check valve extends out of the other end of the passage beyond the other face of the piston.

4. The structure according to claim 1 wherein a pressure relief valve and fluid accumulator are provided and are connected to the circuit for receiving fluid therefrom when the pressure created in the circuit by operation of the operator of either master assemblage exceeds a predetermined maximum value, and are operative for feeding makeup fluid back into the circuit when said pressure in the circuit is reduced below said maximum value.

5. The structure according to claim 1 wherein the bypass circuit of the slave assemblage comprises two passages separate from each other, the check valves are in the passages, respectively, and each, when its plug is seated closes its associated passage and when its plug is unseated opens its associated passage.

6. The structure according to claim 1 wherein a plurality of reversible slave assemblages are provided, and the cylinders thereof connected in series with each other in said circuit.

7. The structure according to claim 1 wherein the conduits are tubes of synthetic organic plastic having a predetermined coefficient of expansion and contraction under changes in temperature;

the hydraulic fluid in the circuit has a predetermined coefficient of expansion and contraction under said changes; and

the differential between said coefficient of the fluid and the coefficient of each tube is so small as to have a negligible effect on the synchronization of the assemblages.

8. The structure according to claim 7 wherein the tubing is Nylon and the fluid is water and glycol.

9. The structure according to claim 1 wherein each check valve of each master assemblage is a conventional automobile tire valve, and each bypass circuit of each master assemblage connects the check valves of the associated master assemblage together at the plug sides of the valve seats, and connects the check valves at the opposite sides of the seats to the associated cylinder at opposite sides of the piston, respectively.

10. A piston and cylinder assemblage, for a linear selfsynchronizing master-slave remote control, comprising:

a cylinder;

a piston reciprocable therein;

mechanical drive means exteriorly of the cylinder and connected to the piston for moving the piston, thereby driving the piston in opposite directions, selectively, for generating hydraulic power;

a bypass circuit connecting the opposite ends of the cylinder together in bypassing relation to the piston;

a pair of normally closed check valves in series with each other in the bypass circuit and having spring seated plugs, respectively and being operative upon concurrent unseating of both plugs to open the bypass circuit;

the check valve plugs unseating in opposite directions relative to the flow of fluid through the bypass circuit so that a differential in fluid pressure in the master cylinder drives the piston thereof away from the higher pressure end of the cylinder toward the lower pressure end of the cylinder, and urges to unseated position the one of the plugs nearest the higher pressure end of the cylinder along the path of flow through the bypass circuit, and urges the plug nearest the low-pressure end of the cylinder along said path of flow to seated position;

mechanical trip means associated with the master assemblage;

the mechanical trip means being operative upon movement of the piston a predetennined distance toward the lower pressure end of the cylinder, to engage and unseat mechanically the one of the associated plugs which is urged to seated position by said differential in fluid pressure. 

1. A linear self-synchronizing master-slave remote control comprising: a plurality of reversible, hydraulic power generating, master piston and cylinder assemblages and a reversible slave piston and cylinder assemblage responsive to the hydraulic power generated by the master piston and cylinder assemblages; each assemblage including a cylinder having an inlet and an outlet and a piston reciprocable in the cylinder; operators mechanically connected to the master pistons, respectively, and movable independently of each other, each in opposite directions, selectively, for thereby driving its associated piston in opposite directions, selectively, for generating hydraulic power; means for connecting the slave piston to a mechanism to be driven thereby; conduits connecting all oF the cylinders in series in a closed hydraulic circuit; bypass circuits in the master assemblages, respectively, each bypass circuit, when open, connecting the opposite ends of the associated master cylinder directly to each other; a pair of normally closed check valves in series with each other in each bypass circuit and having spring seated plugs, respectively, and being operative upon concurrent unseating of both plugs to open their associated bypass circuit; the check valve plugs of each pair unseating in opposite directions relative to the flow of fluid through their associated bypass circuit so that a differential in fluid pressure in the associated master cylinder drives the piston thereof away from the higher pressure end of the cylinder toward the lower pressure end of the cylinder, and urges to unseated position the one of the plugs nearest the higher pressure end of the cylinder along the path of flow through the bypass circuit, and urges the plug nearest the low-pressure end of the cylinder along said path of flow to seated position; mechanical trip means associated with the master assemblages, respectively; the mechanical trip means of each master assemblage being operative upon movement of the piston thereof a predetermined distance toward the lower pressure end of the cylinder thereof, to engage and unseat mechanically the one of the associated plugs which is urged to seated position by said differential in fluid pressure; a slave cylinder bypass circuit in the slave assemblage and operative when open to connect opposite ends of the slave cylinder to each other; and a pair of normally closed check valves in the slave cylinder bypass circuit, each valve having a spring seated plug, and said plugs normally closing the slave cylinder bypass circuit, one of said plugs being unseatable and thereby opening the associated bypass circuit and the other being urged concurrently to seated position by a fluid pressure differential above a predetermined normal operating differential in the slave cylinder at one side of the slave piston; the other of said plugs being unseatable and thereby opening the associated bypass circuit and the one plug being urged concurrently to seated position by a fluid differential pressure above said predetermined normal operating differential in the slave cylinder at the opposite side of the slave piston.
 2. The structure according to claim 1 wherein, in each master assemblage, unseating stems are connected to the plugs, respectively, of the check valves; said stems are exposed at opposite sides, respectively, of the piston; and said mechanical trip means include trip members in the cylinder at opposite sides of the piston, respectively; each member is engageable with the associated stem, which is exposed at the same side of the piston as the trip member, so as to move the engaged stem to plug unseating position upon movement of the piston a predetermined distance toward the end of the cylinder on the same side of the piston as the associated member and stem.
 3. The structure according to claim 2 wherein the bypass circuit of each master assemblage comprises a passage extending endwise through the piston, said check valves are mounted in the passage so as to be in sealing relation thereto when in closed position; the stem of one check valve extends out of one end of the passage beyond the adjacent face of the piston; and the stem of the other check valve extends out of the other end of the passage beyond the other face of the piston.
 4. The structure according to claim 1 wherein a pressure relief valve and fluid accumulator are provided and are connected to the circuit for receiving fluid therefrom when the pressure created in the circuit by operation of the operator of either master assemblage exceeds a predetermined maximum value, and are operative for feeding makeup fluid back into the circuit when said pressure in the circuit is reduced below said maximum value.
 5. The structurE according to claim 1 wherein the bypass circuit of the slave assemblage comprises two passages separate from each other, the check valves are in the passages, respectively, and each, when its plug is seated closes its associated passage and when its plug is unseated opens its associated passage.
 6. The structure according to claim 1 wherein a plurality of reversible slave assemblages are provided, and the cylinders thereof connected in series with each other in said circuit.
 7. The structure according to claim 1 wherein the conduits are tubes of synthetic organic plastic having a predetermined coefficient of expansion and contraction under changes in temperature; the hydraulic fluid in the circuit has a predetermined coefficient of expansion and contraction under said changes; and the differential between said coefficient of the fluid and the coefficient of each tube is so small as to have a negligible effect on the synchronization of the assemblages.
 8. The structure according to claim 7 wherein the tubing is Nylon and the fluid is water and glycol.
 9. The structure according to claim 1 wherein each check valve of each master assemblage is a conventional automobile tire valve, and each bypass circuit of each master assemblage connects the check valves of the associated master assemblage together at the plug sides of the valve seats, and connects the check valves at the opposite sides of the seats to the associated cylinder at opposite sides of the piston, respectively.
 10. A piston and cylinder assemblage, for a linear self-synchronizing master-slave remote control, comprising: a cylinder; a piston reciprocable therein; mechanical drive means exteriorly of the cylinder and connected to the piston for moving the piston, thereby driving the piston in opposite directions, selectively, for generating hydraulic power; a bypass circuit connecting the opposite ends of the cylinder together in bypassing relation to the piston; a pair of normally closed check valves in series with each other in the bypass circuit and having spring seated plugs, respectively and being operative upon concurrent unseating of both plugs to open the bypass circuit; the check valve plugs unseating in opposite directions relative to the flow of fluid through the bypass circuit so that a differential in fluid pressure in the master cylinder drives the piston thereof away from the higher pressure end of the cylinder toward the lower pressure end of the cylinder, and urges to unseated position the one of the plugs nearest the higher pressure end of the cylinder along the path of flow through the bypass circuit, and urges the plug nearest the low-pressure end of the cylinder along said path of flow to seated position; mechanical trip means associated with the master assemblage; the mechanical trip means being operative upon movement of the piston a predetermined distance toward the lower pressure end of the cylinder, to engage and unseat mechanically the one of the associated plugs which is urged to seated position by said differential in fluid pressure. 